Cyclic hematopoiesis (CH) is an autosomal dominant disease in which the regulatory clock for blood cell production is perturbed. At 21 day intervals, affected individuals develop severe neutropenia, fever, and life.- threatening infections, due to interrupted blood cell formation. We have mapped the gene of cyclic hematopoiesis to a zero CM genetic interval on chromosome 19p13.3 with lod score 8.40 at theta of 0.06. The physical interval is approximately 900 kb. CH is genetically homogenous in the 11 families we have analyzed. The goal of Project 3 is clone the CH gene and define the molecular pathogenesis of cyclic hematopoiesis. The Specific Aims are: 1) To identify the locus of autosomal dominant cyclic hematopoiesis by a) genotyping of families using new set of markers, b) performing high resolution mapping using new markers we will identify in the about 900 kb interval in which the CH gene has been mapped, c) perform linkage disequilibrium, studies utilizing the 46 sporadic cases of CH we have already identified. 2) To perform mutational analyses of genes in the critical region to identify potentially novel genes in the critical region. a) Identify candidate genes. b) In collaboration with project 1, use "virtual Northerns" of the critical region to identify potentially novel genes expressed in cells of the hemopoietic lineage which map within the critical region. c) Use established mutational analysis methods to identify the CH mutations in the affected families and sporadic cases. 3) Perform structural and functional studies using the cloned CH gene, b) clone the canine homolog in order to test whether cyclic hematopoiesis in the dog is due to a mutation of the CH gene, c) clone the murine homolog, d) characterize CH gene expression in hematopoietic and non-hematopoietic lineages, e) define regulatory elements of the gene and its functional domains, f) produce transgene mouse models using transgenic, knock-out or knock-in technologies, g) test mechanisms of CH gene action in hematopoiesis and f) test effects of the CH mutation in mature hemopoietic and non-hemopoietic cells and 4) continue collecting new CH families in order to determine the spectrum of mutations that produce the CH genotypes.